In recent years, portable products using battery, such as cameras, digital video cameras, mobile phones, laptops and so on, have been widely used in people's daily life. Developing trends and demands of the battery product industry requires the batteries to have smaller size, lighter weight and longer service life. Thus, it is an urgent need for the industry to develop suitable power supply products for portable electronic devices, particularly a secondary battery having high energy density and light weight.
During initial charging/discharging of a lithium-ion battery, a layer of SEI film will be formed on a surface of a negative electrode of the lithium-ion battery. If the formed SEI film is too thick and has higher resistance, a lithium ion cannot pass through the SEI film and thus lithium precipitation will occur. During cycling, if the formed SEI film is not compact and stable enough, the formed SEI film will gradually dissolve or rupture, and the negative electrode being exposed will continue reacting with the electrolyte, which causes that the electrolyte is consumed and the battery capacity is decreased. Thus, the quality of the SEI film is substantially crucial to performance of the lithium-ion battery. Since quality and film resistance of the SEI film vary due to different additives or different amounts of the same additive in the electrolyte, it will be necessary to improve the quality of the SEI film by adjusting the additive and the amount thereof to obtain a lithium-ion battery with high performance.
In view of the above, the present application is provided.